The industry is running out of cost-effective ways to make small patterns in integrated circuit (IC) designs, especially hole structures. FIG. 1 illustrates schematically the need for such small hole structures. An array of lines 10 form a topography 20 on a substrate. The lines 10 need to be cut in a typical design, for example, a 10 nm node design. Square-shaped holes 12 and rectangle-shaped holes 14 would be patterned to allow access to the lines 10 for cutting. As the area of the entire pattern shrinks, smaller holes 12, 14 must be patterned, and the space between holes gets tighter as well. Historically, lithographic applications have been able to print all of these holes in a single print. However, currently, multiple exposure passes are required to print the different holes because they are so close together and so small, and by the time the 10 nm node arrives, it is likely that as many as four masks will be required to print even this simple geometry.
Block copolymers (BCPs) are being investigated for their use in making fine patterns because they can thermodynamically form very small domains of regular structures currently used in semiconductor patterning (e.g., cylinder or line/space patterns). Typically, in these systems, the assembly of the BCP is directed by an external driving force. One such method for directing the BCP assembly is through the use of physical templates. However, there is a need for methods for directing the assembly of BCPs that enable greater control of the interfaces of the blocks to allow for more precise creation of the exact shapes needed to make fine circuit patterns.